The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Interactive digital maps, which various geographic applications display on computing devices, generally depict numerous geographic features, such as roads, outlines of countries and towns, bodies of water, buildings, etc. Geographic features displayed as part of a digital map can have different appearance at different levels of magnification of the digital map, commonly referred to as “zoom levels.” A digital map can be made up of several tiles, or portions of a certain fixed size, typically dependent on the zoom level.
Generally speaking, map servers can provide map data to client devices as map images in raster formats, according to which map images are described in terms of pixels, or in a scalable formats that rely on mathematical descriptions of shapes (e.g., the vector graphics format). In the former case, map images are generally ready for display on client devices. In the latter case, client devices first interpret map data locally to generate raster map images, at a relatively high computational cost, and only then display these map images.
Transmitting map data in an image format generally takes up a significant amount of bandwidth, and compressing map image data either results in a loss of quality users can easily notice, or requires the use of lossless algorithms that do not provide significant savings in bandwidth. Meanwhile, the proliferation of high-resolution screens in portable and non-portable devices causes content providers, including providers of interactive digital maps, to transmit large, high-resolution images to client devices.